Testing

ClojureScript now ships with a port of clojure.test in the form of
cljs.test. It attempts to preserve most of the functionality provided
by clojure.test along with enhancements for asynchronous testing in a
single threaded environment.

Most of the functionality is provided via macros as cljs.test relies
on compiler reflection and static vars to provide most of its
functionality.

For example your testing ns form will probably look something like the
following:

Writing Tests

You can write tests with cljs.test/deftest and cljs.test/is same as
with clojure.test.

For example here is a trivial test with one assertion:

(deftest test-numbers
(is (= 1 1)))

Running Tests

You can run tests by using the cljs.test/run-tests macro. This may be
done in your REPL or at the end of your file. If you have many test
namespaces it’s idiomatic to create a test runner namespace which
imports all of your test namespaces and then invokes run-tests.

You may have to add (enable-console-print!) before calling run-tests

Fixtures

You can declare fixtures with the cljs.test/use-fixtures macro. You
can declare either :once fixtures or :each fixtures. :once
fixtures are run only around all tests within a namespace. :each
fixtures are run around each test. Unlike clojure.test fixtures are
split into two parts :before and :after. This is so that fixtures
will work correctly even when used asynchronously.

(use-fixtures :once
{:before (fn [] ...)
:after (fn [] ...)})

Async Testing

As client-side code tends to be highly asynchronous and JavaScript is
single-threaded, it’s important that cljs.test provide asynchronous
testing support. You can use the cljs.test/async macro to create an
asynchronous block. If you write an asynchronous test the last value you
return must be the async block.

done is a function that you may invoke when you are ready to
relinquish control and allow the next test to run. done can be called
anything, but it probably makes sense to keep to the convention. All of
your testing code must be in the async block. If you launch multiple
asychronous processes in your async block you will need to coordinate
them. This is a good reason to use cljs.core.async:

Async Fixtures

In this case :before will need to complete before any test can run.
:after will complete immediately after all tests have run since it
does not use an async block.

Detecting Test Completion & Success

Often it’s useful to be able to run some code after all tests have
completed successfully (or unsuccessfully). Because tests may run async
cljs.test/run-tests does not return a meaningful value. You can
however add a test report event listener by adding a method to the
cljs.test/report multimethod.